java 判断日期为第几天

Posted 2021-12-22 DQ_CODING

题目1

编写程序：从键盘上输入2019年的“month”和“day”，要求通过程序 输出输入的日期为2019年的第几天。

代码1

从12月往下加日期数

package l1_switch_case;
import java.util.Scanner;
public class SwitchDemo4 
    public static void main(String[]args)
        Scanner scanner=new Scanner(System.in);
        int month=scanner.nextInt();
        int day=scanner.nextInt();
        int date=0;
    /*    //方式1：冗余
        switch (month)
            case 1:
                date=day;
                break;
            case 2:
                date=31+day;
                break;
            case 3:
                date=31+28+day;
                break;
            case 4:
                date=31+28+31+day;
                break;
            case 5:
                date=31+28+31+30+day;
                break;
            case 6:
                date=31+28+31+30+31+day;
                break;
            case 7:
                date=31+28+31+30+31+30+day;
                break;
            case 8:
                date=31+28+31+30+31+30+31+day;
                break;
            case 9:
                date=31+28+31+30+31+30+31+31+day;
                break;
            case 10:
                date=31+28+31+30+31+30+31+31+30+day;
                break;
            case 11:
                date=31+28+31+30+31+30+31+31+30+31+day;
                break;
            case 12:
                date=31+28+31+30+31+30+31+31+30+31+30+day;
                break;
        */

        switch (month)
            case 12:
                date+=31;
            case 11:
                date+=31;
            case 10:
                date+=30;
            case 9:
                date+=31;
            case 8:
                date+=31;
            case 7:
                date+=30;
            case 6:
                date+=31;
            case 5:
                date+=30;
            case 4:
                date+=31;
            case 3:
                date+=28;
            case 2://加上2月份前面一个月的天数
                date+=31;
            case 1:
                date+=day;

        
        System.out.println(date);
        scanner.close();
    

题目2

从键盘分别输入年、月、日，判断这一天是当年的第几天
注：判断一年是否是闰年的标准：
可以被4整除，但不可被100整除
或
可以被400整除

代码2-写法1

package l1_switch_case;

import java.util.Scanner;

public class SwitchDemo5 
    public static void main(String[] args) 
        Scanner scanner = new Scanner(System.in);
        int year = scanner.nextInt();
        int month = scanner.nextInt();
        int day = scanner.nextInt();
        int date = 0;
        int february = 0;
        if ((year % 400 == 0) || (year % 4 == 0 && year % 100 != 0)) 
            february = 29;
         else 
            february = 28;
        
        switch (month)
            case 12:
                date+=31;
            case 11:
                date+=31;
            case 10:
                date+=30;
            case 9:
                date+=31;
            case 8:
                date+=31;
            case 7:
                date+=30;
            case 6:
                date+=31;
            case 5:
                date+=30;
            case 4:
                date+=31;
            case 3:
                date+=february;
            case 2://加上2月份前面一个月的天数
                date+=31;
            case 1:
                date+=day;

        
        System.out.println(date);
        scanner.close();
    

代码2-写法2

package l1_switch_case;

import java.util.Scanner;

public class SwitchDemo6 
    public static void main(String[] args) 
        Scanner scanner = new Scanner(System.in);
        int year = scanner.nextInt();
        int month = scanner.nextInt();
        int day = scanner.nextInt();
        int date = 0;
       
       
        switch (month)
            case 12:
                date+=31;
            case 11:
                date+=31;
            case 10:
                date+=30;
            case 9:
                date+=31;
            case 8:
                date+=31;
            case 7:
                date+=30;
            case 6:
                date+=31;
            case 5:
                date+=30;
            case 4:
                date+=31;
            case 3:
                if ((year % 400 == 0) || (year % 4 == 0 && year % 100 != 0)) 
                    date+= 29;
                 else 
                    date+ = 28;
                
            case 2://加上2月份前面一个月的天数
                date+=31;
            case 1:
                date+=day;

        
        System.out.println(date);
        scanner.close();